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[Xen-devel] Re: scrubbing pages on vm pause

To: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Subject: [Xen-devel] Re: scrubbing pages on vm pause
From: Joanna Rutkowska <joanna@xxxxxxxxxxxxxxxxxxxxxx>
Date: Tue, 25 May 2010 16:19:48 +0200
Cc: "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Rafal Wojtczuk <rafal@xxxxxxxxxxxxxxxxxxxxxx>
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On 05/25/2010 04:13 PM, Keir Fraser wrote:
> On 25/05/2010 15:12, "Joanna Rutkowska" <joanna@xxxxxxxxxxxxxxxxxxxxxx>
> wrote:
>>> New domains are not guaranteed to receive zeroed memory. The only guarantee
>>> Xen provides is that when it frees memory for a *dead* domain, it will scrub
>>> the contents before reallocation (it may not write zeroes however, in a
>>> debug build of Xen for example!). Other memory pages the domain freeing the
>>> pages must scrub them itself before freeing them back to Xen.
>> And what happens when we pause and save a domain? Are the pages zero-out
>> by xen in that case?
> If the original domain is subsequently destroyed then yes, Xen zeroes the
> pages.

Let's consider this scenario:

xm save domain1

xm create domain2

Can the domain2 get *unscrubbed* pages that were previously used by
domain1, but were not scrubbed properly by domain1?


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